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|Posted on February 7, 2013 at 7:45 PM|
Richard Davidson lecture on the impact of mental training on the neural circuits of emotion and attention. Watch here. (min. 5.08)
Circuits of emotion
Sensory information travels from the sensory organs, through relay centres (sensory thalamus) to the cortex. Once the relevance of this information is processed (is it safe or dangerous), this is transmitted to the the visceral organs (heart and the lungs) and to the muscles in our face and body. If we perceive a threatening stimulus (i.e) a predator, our heart beats faster and hour lungs work harder, etc. The information about the state of the viscera and the body then travels back to the brain. It is only when the brain detects the changes in our body that the experience of emotion arises. This is an influential view espoused by William James in the "Principles of psychology". The fact that our perception of emotion is reliant of information from the body was proven through an experiment in which people who had botox injected in their forehead (in muscles associated with the expression of sadness) were tested before and after. The test showed that the lack of signal feedback from these muscles to the brain changed the emotional response of the person (they experienced less sadness).
James Papez was the first to describe a model of the circuit in the brain associated with emotion. His model included the hippocampus, the hypothalamus, the anterior thalamus and the cingulate gyrus.This was the first time that it was suggested that emotion is processed in parts of the brain that lie below the cortex. Later on, studies on patients with lesions to the prefrontal cortex showed that the cortex (the medial prefrontal part) is actually involved in emotional processing.
In the modern understanding, the capacity to regulate our emotions is associated with the prefrontal cortex. No other species can voluntarily regulate their emotions in the way humans do.
Emotion as a process is distributed throughout a circuit and different areas of the brain interact to create emotion (i.e. the limbic system and the prefrontal cortex. However there is no single site in the brain about which we can say: that is where emotion resides. There are circuits in the brain for positive emotions and circuits that process negative emotion.
Stress changes the structure of the brain, particularly the hippocampus, amygdala and orbito-frontal cortex. When an animal is chronically stressed the nervous cells in the hippocampus shrink shrink (fewer dendrites), whereas cells in the amygdala apear to have more ramifications. (Davidson & McEwan, Nature neuroscience, 2012)
Networks in the brain important for attention
Attention has different atributes and some can be distinguished in terms of circuits in the brain. There are three types of attention: alerting, orienting and executive control. Alerting occurs for instance when there is a big loud noise. Something happens in the environment and our attention is pulled towards it. Orienting is the capacity to direct your attention mentally to different senses. Executive control is about resisting distractions and directing our mind to focus on one thing and inhibit the distractive influences that come from somewhere else. There are parts of the brain involved with these attention functions that overlap with emotion. This is not surprising because it is emotionally relevant information in our environment that captures our attention. We do not become alerted to neutral stimuli.
The impact of contemplative training on networks important in attention
Children who have attention deficit hyperactivity disorder are very variable in how they pay attention. In a study in which participants practiced Vipassana meditation for three months, it was shown that this practice greatly helped reduce this variability of attention (Lutz et al. 2009, Neuroscience).